From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from szxga01-in.huawei.com ([58.251.152.64]:62463 "EHLO szxga01-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933208AbbFXBrY (ORCPT ); Tue, 23 Jun 2015 21:47:24 -0400 Message-ID: <558A0C1F.6010405@huawei.com> Date: Wed, 24 Jun 2015 09:47:11 +0800 From: Yijing Wang MIME-Version: 1.0 To: Bjorn Helgaas CC: Subject: Re: [PATCH 3/3] PCI: Use usleep_range() instead of msleep() for better accuracy References: <1434700666-6346-1-git-send-email-wangyijing@huawei.com> <1434700666-6346-4-git-send-email-wangyijing@huawei.com> <20150619171249.GK7710@google.com> In-Reply-To: <20150619171249.GK7710@google.com> Content-Type: text/plain; charset="UTF-8" Sender: linux-pci-owner@vger.kernel.org List-ID: On 2015/6/20 1:12, Bjorn Helgaas wrote: > On Fri, Jun 19, 2015 at 03:57:46PM +0800, Yijing Wang wrote: >> Msleep < 20ms can sleep for up to 20ms, see >> Documentation/timers/timers-howto.txt, so we could >> use usleep_range instead. >> >> Signed-off-by: Yijing Wang >> --- >> drivers/pci/hotplug/pciehp_hpc.c | 2 +- >> 1 files changed, 1 insertions(+), 1 deletions(-) >> >> diff --git a/drivers/pci/hotplug/pciehp_hpc.c b/drivers/pci/hotplug/pciehp_hpc.c >> index daf54be..4553728 100644 >> --- a/drivers/pci/hotplug/pciehp_hpc.c >> +++ b/drivers/pci/hotplug/pciehp_hpc.c >> @@ -118,7 +118,7 @@ static int pcie_poll_cmd(struct controller *ctrl, int timeout) >> } >> if (timeout < 0) >> break; >> - msleep(10); >> + usleep_range(10000, 11000); > > timers-howto.txt also says to use msleep for 10ms+ delays, so the guidance > is a bit ambiguous. > > This particular delay does not need to be precise, and if we delay 20ms > instead of 10ms (1/50th of a second vs 1/100th of a second), I don't think > it makes any difference at all. > > If we *did* make a change here, I think we should use a range of at least > 10ms. There's no need to tighten the wakeup time to the 1ms window between > 10ms and 11ms. Any time in the range of 10ms to 50ms would probably be > fine. > > But I don't think a change here is necessary, and it does make it a bit > harder to analyze the code because we have some things in microseconds and > others in milliseconds. OK， I got it, thanks for your explanation. Thanks! Yijing. > >> timeout -= 10; >> } >> return 0; /* timeout */ >> -- >> 1.7.1 >> > > -- Thanks! Yijing